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Variance | The Shortcut Formula

It’s not much of a shortcut, but some exams will ask you specifically to use the shortcut formula, so I demonstrate it here using the same data from question 1c)

Shortcut Variance formula for discrete random variables is:

Variance of X:

NOTE: Whether you use this formula or the regular variance formula is up to you – They give the EXACT same results.


Test your understanding: